1H-pyrazolo[5,1-c]-1,2,4-triazole compounds are useful compounds as magenta couplers for silver halide color photographic materials. As processes for synthesizing these compounds, the following synthesis processes are hitherto known.
A first synthesis process is disclosed in U.S. Pat. No. 3,725,067, British Patent No. 1,252,418, or Journal of the Chemical Society, Parkin I (9177), pages 2047 to 2052. In this process, a 5-hydrazino-1H-pyrazole-4-carboxylate compound can be acylated to obtain a 5-acylhydrazino-1H-pyrazole-4carboxylate compound, and it is then heated together with phosphorous oxychloride for a long period of time under reflux to produce a 1H-pyrazolo[5,1-c]-1,2,4-triazole compound. However, in this process, there are two processing steps and the ring-closing step requires a higher temperature and a long reaction time. The yield of some compounds decreases and therefore improvements of the process are desired.
A second process is described in JP-A ("JP-A" means unexamined published Japanese patent application) No. 158283/1987. In this process, a 5-hydrazino-1H-pyrazole compound is acylated to obtain a 5-acylhydrazino-1H-pyrazole compound, which is reacted with thionyl chloride, followed by a ring-closure reaction in the presence of an alcohol, to produce a 1H-pyrazolo[5,1-c]-1,2,4-triazole compound. However, this process also is carried out in two steps and the reaction medium has to be replaced in the dehydration-ring-formation reaction of the 5-acylhydrazino-1H-pyrazole compound, so that the procedure is complex.
Furthermore, the above synthesis processes are both required to be carried out under strong acid conditions, and the yield of some compounds decreases extremely under these conditions.
A third synthesis process is described in JP-A No. 233285/1989. That is, either an imide acid ester or an orthoester is reacted with 5-hydrazino-1H-pyrazole to synthesize a 1H-pyrazolo[5,1-c]-1,2,4-triazole compound in one step. In this process, it is desired to improve further the yield.
As described above, the conventional processes for obtaining a 1H-pyrazolo[5,1-c]-1,2,4-triazole compound using a 5-hydrazino-1H-pyrazole as a raw material have such problems that the number of the processing steps is large, the reaction time is long, the procedure is complex, or the yield is low.